1. Field of the Invention
The present invention relates to a picture signal encoding system for encoding and transmitting a picture signal in the form of an encoded bit stream compressed with a variable-length code, a picture recognition system for recognizing an object in the process of encoding an picture signal, and a picture signal decoding system for receiving such an encoded bit stream to decode it into a picture signal and for further having a function to eliminate the errors that take place in the picture signal.
2. Description of the Prior Art
Recently, information communication terminals or stations have abruptly been coming into multimedia, and even in the field of telephones, various additive values on a digital data transmission really need to be created for the future business development. Particularly, in the field of PHS (Personal Handy Phone System), studies have on a full scale been made for the purpose of, in addition to the conventional audio and character information communications, transmitting natural still pictures and motion pictures. Thus, the telephones are also expected to come into multimedia in near future. However, a problem still remains in that difficulty is encountered in the transmission of TV images of a signal quantity corresponding to approximately 166 Mbps in a non-compressed condition through the PHS (of 384 kbps, 32 or 48 kbps is assigned for the image) or through the existing transmission route (10 kbps) of a telephone line.
One possible solution may be to employ the motion picture compression technique for the conventional TV conference systems or video CD systems. However, for example, the current TV conference standard or specification ITU-T/H.261 is made to cover 64 kbps to 2 Mbps while ISO/MPEG1 is made to accept approximately 1.5 Mbps, and hence these standards can not cope with an extremely low rate transmission below 64 kbps. Incidentally, although the H. 263 standard advised in November, 1995 is made to handle 4.8 kbps to 64 kbps, its content is still unknown to make difficult the recognition of its method. Besides, that standard does not accept the connectability with the H.261.
Moreover, such a motion picture compression technique is principally for wire-based communications and can not completely demonstrate the countermeasures against the level (approximately 10.sup.-2 to 10.sup.-3) of the data transmission error that will take place in the wireless communications such as a mobile communication. Generally, the wireless systems employ the so-called demand refreshing method implementing a retransmission request based on ARQ (Automatic Repeat Request). There is a problem which arises with the use of the ARQ, however, in that in the reception side the freeze of the picture is unavoidable before the completion of the retransmission of the image information. For this reason, if the radio transmission circumstances go worse, the picture-frozen state can continue to virtually make impossible the motion picture transmission.
On the other hand, for the still picture transmission, there has been proposed a rate-controlling way in which the data are classified in groups in accordance with their degrees of significance, but it still has not been put to practical use. Further, for the transmission rate of approximately 384 kbps, there has been reported a method which copes with the transmission errors by means of a data transmission sequence and an error correcting code, which however is not a candidate for the extremely low rate wireless transmission below 64 kbps.